摘要: Plastic pollution is now recognised as a growing concern for both the environment and associated biota. Consequently, a plethora of scienti fic reports are being produced regarding the occurrence, distribution, and transfer pathways of litter particles. However, there are scienti fic gaps that need to be filled regarding microand nanoplastic impacts on marine and freshwater organisms. This Special Issue (SI) aimed to provide an update on plastic pollution and its consequences on aquatic ecosystems, with a particular focus on biological domains, by adopting a multidisciplinary perspective. Several research articles and reviews were collected, focusing on the origin, fate, and effects of plastics in marine and freshwater environments, along with their interactions with biotic components. We believe this SI will contribute to the development of new studies on plastic pollution and the elaboration of science-based policies at different levels of our modern society.

摘要: The use of environmental DNA (eDNA) has significantly revolutionized studies in biodiversity science. A crucial innovation of eDNA-based biodiversity assessment is the ability to detect species through genetic materials released by organisms into their environments, without the need for direct observation or capture (i.e., organisms remain unseen). The fact that organisms remain unseen has many pros and cons, many of which have been largely recognized and technically addressed or managed. However, two recent studies have both highlighted another critical issue regarding eDNA-based biodiversity assessments: the prevalence of overlooked eDNA contamination originating from human activities, such as the release of treated wastewater into aquatic ecosystems. Such eDNA contamination derived from human activities can lead to significant false positive errors in eDNA-based biodiversity assessments, particularly in human-disturbed ecosystems such as urban and coastal environments. Here I discuss the causes and consequences of eDNA contamination, stressing that this widespread but often neglected issue can substantially affect both eDNA-based theoretical studies and applied biodiversity management. Additionally, I propose several potential technical solutions to minimize its negative impacts, including well-designed sampling strategies, a deeper understanding of eDNA persistence and its spread in local waterbodies, and the use of environmental RNA (eRNA). Given that eDNA contamination can significantly impact ecosystems such as urban and coastal environments where biodiversity provides essential ecosystem services, I call for precautionary approaches and technical efforts to mitigate false positives derived from eDNA contamination in biodiversity assessments in these ecosystems.

摘要: The conversion of natural ecosystems to human land use is a primary cause of worldwide biodiversity loss and trophic structure changes in ecosystems. We investigated the effect of human land use at different spatial extents and aquatic trophic state on basal energy sources, food chain length (FCL), and the isotopic niche of apex fish in four large neotropical wetlands. We had two hypotheses. (i) Increased regional human land is negatively associated with the contributions of allochthonous energy sources, FCL, and isotopic niche. (ii) Trophic state is directly associated with FCL, autochthonous energy source, and niche area. We found that C3 riparian vegetation was the primary energy source for apex consumers. Human land uses in a 5000 m buffer were directly associated with allochthonous basal-energy source assimilation and niche area and indirectly with FCL. FCL was shorter in environments with more human land use and allochthonous energy source assimilation had an important role on FCL. Therefore, conserving riparian vegetation surrounding water bodies is a crucial protective factor for waters, as it serves as a primary energy source for food webs. Decreased FCL with increased human activity demonstrated the sensitivity of these environments to trophic-link losses from human invasion. Conversely, increased isotopic niche areas in environments with high human activities may be attributed to the introduction of new energy sources from those activities. Hence, the loss of natural cover resulting from human activities is an important factor in aquatic trophic structure changes.

摘要: Non-native freshwater fish species are regarded as a key factor responsible for the degradation of freshwater ecosystems. Although research on China's non-native freshwater fish species has been conducted at the national scale, the spatial distribution and introduction pathways of these species in China remain unclear. To address this knowledge gap, this study compiled a dataset of non-native freshwater fish species across administrative regions in China. We first assessed the number of non-native freshwater fish species by taxonomy, geographical origin, introduction pathway, and province. There were 177 non-native freshwater fish species, belonging to 17 orders, 48 families, and 118 genera. The orders Cypriniformes (33.3%), Perciformes (28.2%), Siluriformes (10.2%), and Salmoniformes (6.2%) accounted for the largest proportion of non-native freshwater fish species. Eighty-nine nonnative species were introduced from other countries or regions, mostly from North America (31 species; 34.8%), Asia (20 species; 22.5%), Africa (13 species; 14.6%), Europe (11 species; 12.4%), and South America (10 species; 11.2%). Aquaculture was the most common introduction pathway. Non-native freshwater fish species were more widely distributed in southwest China. Our study showed that there were obvious differences in the number and composition of non-native freshwater fish species across various provinces in China. The variation in the number of non-native freshwater fish species across provinces in China was attributed to distinct geographical features, development of the aquaculture industry, and efforts to study non-native freshwater fish species. Therefore, comprehensive surveys and studies of non-native freshwater fish species are needed, which are of great importance for the management and control of non-native species invasions.

摘要: Intensive application of chlorine-based disinfectants driven by the COVID-19 pandemic was suspected to be detrimental to receiving water ecosystems, but with little field evidence. We characterized the occurrences of typical disinfectants and microeukaryotic communities in surface waters associated with three wastewater treatment plants (WWTP)-river systems one year after the lockdown in Wuhan, China. Trihalomethanes (THMs) declined from summer 2020 (0.01-1.82 mu g/L) to summer 2021 (0.01-0.95 mu g/L), whereas quaternary ammonium salts (QAs) increased from summer 2020 (0.53-6.35 ng/L) to summer 2021 (8.49-191 ng/L). Biodiversity monitoring with environmental DNA (eDNA) revealed significant temporal variation in microeukaryotic community composition. The monitored disinfectants were correlated with some eukaryotic communities as demonstrated by redundancy analysis. For example, QAs were positively related to Cryptophyta relative abundance, but negatively related to Rotifera relative abundance. A microeukaryote-based multimetric index indicated ecological impairment near the Han River WWTP outlet in 2020. Our findings indicate the influence of heavily used disinfectants on river microeukaryotic communities, and the usefulness of assessing mid-term ecological risks from disinfectants in the post COVID-19 era.

摘要: Carassius auratus herpesvirus (CaHV) is a pathogen isolated from crucian carp (Carassius auratus) associated with high mortality. A diagnosis method that can detect the virus at an early stage, specifically and accurately, is an urgent requirement for the prevention of CaHV transmission. In the present study, a droplet digital PCR (ddPCR) method based on the tumor necrosis factor receptor (TNFR) gene was established to detect and quantify CaHV DNA with high specificity and no cross-reactions with other aquatic viruses. Skin mucus samples were collected from infected crucian carp from Day 1-8 after infection, and positive amplification was detected on the first day by ddPCR (0.54 copies/mu L), whereas the presence of CaHV was not detected by routine PCR until Day 6. Tissue DNA was then collected from the head kidney of 20 fishes which were injected with CaHV and died during the experiment. The five negative samples checked by routine PCR were detected by ddPCR and real-time PCR (qPCR), respectively. The results showed that the positive detection rate of ddPCR (100%) was higher than that of qPCR (40%). The detection limit of the ddPCR was found to be 0.52 copies/mu L, which was much lower than the 50.12 copies/mu L determined by qPCR. Overall, ddPCR offers a highly promising diagnosis method for the absolute quantification of CaHV in carrier fish and samples from the skin mucus and head kidney with low viral concentrations.

摘要: Fishes use environmental resources differently. Snapper ontogenic movements among coastal habitats lead to diverse diets. We investigated the diets of seven snapper species (Lutjanus apodus, L. analis, L. griseus, L. jocu, L. mahogoni, L. synagris, and Ocyurus chrysurus) in three interconnected coastal environments in the western Caribbean: Rio Huach channel, Chetumal/Corozal bay, and the adjacent Xcalak reef lagoon. These three encompass all habitats used by the seven species in the study area. Snapper diets were mostly composed of fish and crustaceans, but dominance of either group varied among the studied habitats; for example, fish were the main prey for L. apodus from the reef lagoon zone, but second in the bay. Snappers are piscivorous-invertivorous mesopredators; the species that relied the most on fishes were L. griseus and L. jocu, whereas O. chrysurus preferred crustaceans. Stomach content results revealed a high degree of dietary overlap among species. Our findings suggested a tradeoff in relative weight between fish and crustaceans as the main food source of snappers at these connected areas, supporting the hypothesis of niche segregation. Our results can be used as a baseline to further our understanding of the ecology and differences in resource use by snapper species in an area undergoing important anthropogenic changes.

摘要: Viral infectious diseases significantly threaten the sustainability of freshwater fish aquaculture. The lack of studies on epidemic transmission patterns and mechanisms inhibits the development of containment strategies from the viewpoint of veterinary public health. This study raises an epidemic mathematical model considering water transmission with the aim of analyzing the transmission process more accurately. The basic reproduction number R0 was derived by the model parameter including the water transmission coefficient and was used for the analysis of the virus transmission. Spring viremia of carp virus (SVCV) and zebrafish were used as model viruses and animals, respectively, to conduct the transmission experiment. Transmission through water was achieved by connecting two aquarium tanks with a water channel but blocking the fish movement between the tanks. With the collected experimental data, we determined the optimal hybrid machine learning algorithm to analyze the transmission process using an established mathematical model. In addition, future transmission was predicted and validated using the epidemic model and an optimal algorithm. Finally, the sensitivity of model parameters and the simulations of R0 variation were performed based on the modified complex epidemic model. This study is of significance in providing theoretical guidance for minimizing R0 by manipulating model parameters with containment measures. More importantly, since the modified model and algorithm demonstrated better perfor-mance in handling freshwater fish transmission problems, this study advances the future application of trans-missible disease modeling with larger datasets in freshwater fish aquaculture.

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摘要: Pharmaceuticals, including non-steroidal anti-inflammatory drugs (NSAIDs), such as indomethacin and ibuprofen, are prevalent pollutants in freshwater ecosystems, raising concerns about their ecological impact. While there is literature about pharmaceuticals in aquatic environments, the effects of both chemical and commercial forms of NSAIDs on aquatic organisms, particularly across generations, remain insufficiently explored. This study aims to bridge this gap by assessing the impact of pure and commercial forms of indomethacin, ibuprofen, and their mixture on Daphnia magna, a key freshwater species. Toxicity curves, enzyme activities, and metabolomics were used as endpoints to assess physiological responses to chronic and transgenerational exposures at an environmentally relevant concentration of 5 mu g/L. Results showed changes in the activities of beta-galactosidase and lipase, while a targeted LC-MS/MS approach revealed distinct metabolic fingerprints as a result of exposure for four generations to the chemical and commercial indomethacin and ibuprofen. Notably, exposure to chemical mixture of the two NSAIDs increased amino acids and biogenic amines, a trend also observed with commercial NSAIDs and their mixture, while the chemical NSAIDs did not have the same impact. This work emphasizes the necessity of ecotoxicological studies with transgenerational exposures as an approach to comprehend the effect of pharmaceutical stressors at low exposure concentrations, using molecular responses in physiology. This approach contributes to the broader mechanistic understanding of the ecological implications of these pharmaceuticals in freshwater ecosystems.